Welcome to Week 4 of Your Pregnancy!
What’s Happening During Week 4:
It is uncertain how sperm finds the egg. Some think the sperm might even have a sense of smell. Once the sperm penetrates the egg and the centre of each unite, the magic of fertilization has taken place. This single cell will develop into trillions of cells, in fact to over 200 types.
At conception baby receives 23 chromosomes from the mother’s egg and 23 chromosomes from the father’s sperm. Baby’s genetic code is stored in these bundles called chromosomes and each chromosome is made of tightly coiled strands of DNA. If you lined up those DNA molecules end to end, a single cell would contain six feet of DNA!
Genes are working subunits of DNA, some are dominant and others are completely hidden. Parents make up an equal contribution to most of our genetic makeup except for the sex chromosome which is determined solely by the father. At the moment of conception much of the future of baby has already been predetermined, certain diseases, disposition, hair and eye colour, each gene or combination of genes that make us physically and genetically unique.
About a day after conception the cell divides for the first time. Every cell in the human body will need it’s own copy of the original genetic blueprint. Chromosomes produce first, making an identical copy of the genetic code. The nucleus splits and the cell divides. This division causes formation of a new structure called a zygote. After more multiplying and dividing takes place the zygote forms into a morula (12 or more cells) and continues to travel down the fallopian tube. After 4 or 5 days this tiny ball of cells arrives into the uterine cavity and at this time endometrial fluid penetrates this morula to create a central cavity. When this happens this new structure is now known as a blastocyst and is equal to 100 cells. The tissue of the blastocyst then divides into two important layers. The outer layer becomes the placenta and the inner layer the embryo. The inner cells are known as stem cells and have the capacity to turn into any one of over 200 types of cells and can grow to become any part of the body.
The embryo is starting to take shape !